/**
 * @class Ext.state.Provider
 * <p>Abstract base class for state provider implementations. The provider is responsible
 * for setting values  and extracting values to/from the underlying storage source. The 
 * storage source can vary and the details should be implemented in a subclass. For example
 * a provider could use a server side database or the browser localstorage where supported.</p>
 *
 * <p>This class provides methods for encoding and decoding <b>typed</b> variables including 
 * dates and defines the Provider interface. By default these methods put the value and the
 * type information into a delimited string that can be stored. These should be overridden in 
 * a subclass if you want to change the format of the encoded value and subsequent decoding.</p>
 */
Ext.define('Ext.state.Provider', {
    mixins: {
        observable: 'Ext.util.Observable'
    },
    
    /**
     * @cfg {String} prefix A string to prefix to items stored in the underlying state store. 
     * Defaults to <tt>'ext-'</tt>
     */
    prefix: 'ext-',
    
    constructor : function(config){
        config = config || {};
        var me = this;
        Ext.apply(me, config);
        /**
         * @event statechange
         * Fires when a state change occurs.
         * @param {Ext.state.Provider} this This state provider
         * @param {String} key The state key which was changed
         * @param {String} value The encoded value for the state
         */
        me.addEvents("statechange");
        me.state = {};
        me.mixins.observable.constructor.call(me);
    },
    
    /**
     * Returns the current value for a key
     * @param {String} name The key name
     * @param {Object} defaultValue A default value to return if the key's value is not found
     * @return {Object} The state data
     */
    get : function(name, defaultValue){
        return typeof this.state[name] == "undefined" ?
            defaultValue : this.state[name];
    },

    /**
     * Clears a value from the state
     * @param {String} name The key name
     */
    clear : function(name){
        var me = this;
        delete me.state[name];
        me.fireEvent("statechange", me, name, null);
    },

    /**
     * Sets the value for a key
     * @param {String} name The key name
     * @param {Object} value The value to set
     */
    set : function(name, value){
        var me = this;
        me.state[name] = value;
        me.fireEvent("statechange", me, name, value);
    },

    /**
     * Decodes a string previously encoded with {@link #encodeValue}.
     * @param {String} value The value to decode
     * @return {Object} The decoded value
     */
    decodeValue : function(value){

        // a -> Array
        // n -> Number
        // d -> Date
        // b -> Boolean
        // s -> String
        // o -> Object
        // -> Empty (null)

        var me = this,
            re = /^(a|n|d|b|s|o|e)\:(.*)$/,
            matches = re.exec(unescape(value)),
            all,
            type,
            value,
            keyValue;
            
        if(!matches || !matches[1]){
            return; // non state
        }
        
        type = matches[1];
        value = matches[2];
        switch (type) {
            case 'e':
                return null;
            case 'n':
                return parseFloat(value);
            case 'd':
                return new Date(Date.parse(value));
            case 'b':
                return (value == '1');
            case 'a':
                all = [];
                if(value != ''){
                    Ext.each(value.split('^'), function(val){
                        all.push(me.decodeValue(val));
                    }, me);
                }
                return all;
           case 'o':
                all = {};
                if(value != ''){
                    Ext.each(value.split('^'), function(val){
                        keyValue = val.split('=');
                        all[keyValue[0]] = me.decodeValue(keyValue[1]);
                    }, me);
                }
                return all;
           default:
                return value;
        }
    },

    /**
     * Encodes a value including type information.  Decode with {@link #decodeValue}.
     * @param {Object} value The value to encode
     * @return {String} The encoded value
     */
    encodeValue : function(value){
        var flat = '',
            i = 0,
            enc,
            len,
            key;
            
        if (value == null) {
            return 'e:1';    
        } else if(typeof value == 'number') {
            enc = 'n:' + value;
        } else if(typeof value == 'boolean') {
            enc = 'b:' + (value ? '1' : '0');
        } else if(Ext.isDate(value)) {
            enc = 'd:' + value.toGMTString();
        } else if(Ext.isArray(value)) {
            for (len = value.length; i < len; i++) {
                flat += this.encodeValue(value[i]);
                if (i != len - 1) {
                    flat += '^';
                }
            }
            enc = 'a:' + flat;
        } else if (typeof value == 'object') {
            for (key in value) {
                if (typeof value[key] != 'function' && value[key] !== undefined) {
                    flat += key + '=' + this.encodeValue(value[key]) + '^';
                }
            }
            enc = 'o:' + flat.substring(0, flat.length-1);
        } else {
            enc = 's:' + value;
        }
        return escape(enc);
    }
});